Hurricane Flossie Winds: 65 kt
Pressure: 991 mbar
Advisory 9 / 2:00 PM PDT Tuesday, July 30, 2019

Flossie has finally ascended to hurricane strength. The first few visible images of the day showed that the storm's low-level circulation was on the western edge of its convective mass. However, since about 17z, there has been a dramatic uptick in the intensity and coverage of Flossie's central dense overcast, and for once this feature is displaying some semblance of symmetry. The microwave gods have not been kind to us, so we do not have a good view of the storm's internal workings, but it is hard to imagine that a partial inner core has not yet formed. Satellite intensity estimates are T4.0/65kt from SAB and TAFB, with slightly lower values from UW-CIMSS ADT which is incorrectly assessing the center position. Given the increase in organization this afternoon, the initial intensity is set to 65kt.

There are two features to note on visible imagery this afternoon. One, several outflow boundaries emanated from earlier convection, confirming that mid-level dry air has been the cause of Flossie's strife since yesterday. Two, upper-level outflow is expanding in all directions now, a sign that wind shear has temporarily decreased in the vicinity of the hurricane. Now that Flossie is seemingly in the process of developing an inner core and the upper-level environment has become more conducive, the prospects for quick intensification are increasing. This is despite projections from the SHIPS, LGEM, and GFS which show little change in strength moving forward. In many ways, the evolution of Flossie and its model forecasts is similar to what we just experienced with Hurricane Erick. In that case, the best model was the HWRF, which brings Flossie to high-end Category 4 intensity via its most recent run. SHIPS rapid intensification indices are not particularly elevated, but this too was the case for Erick last night preceding its explosive intensification episode. My gut feeling is that Flossie is destined for significant strengthening in the short term, and the intensity forecast has been raised in the short term. By the end of the forecast period, cold waters and drier air will induce weakening.

I do not know what else to say in terms of the track forecast. Flossie is positioned on the southwestern side of a broad mid-level ridge to its north. This ridge should remain in place through the forecast period, steering the hurricane on a west-northwest course for the remainder of the forecast period. On that track, Flossie may begin to approach the Hawaiian Islands after day 5, although it is expected to be quickly-weakening cyclone by that time. This is something to watch in days to come.


INIT 30/2100Z 65 KT 75 MPH

12H 31/0600Z 75 KT 85 MPH

24H 31/1800Z 90 KT 105 MPH

36H 01/0600Z 110 KT 125 MPH

48H 01/1800Z 105 KT 120 MPH

72H 02/1800Z 100 KT 115 MPH

96H 03/1800Z 85 KT 100 MPH

120H 04/1800Z 65 KT 75 MPH

Forecaster TAWX14
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